1. Field of the Invention
This invention relates to a method of varying or selecting optical properties of a body, and to various applications of the method, such as control of optical devices, information recording media and methods and apparatus for recording, erasing and reproducing information.
2. Description of the Prior Art
One technique for providing a high density of optical recording is the method of "photochemical hole burning" (hereinafter referred to as PHB) as described in U.S. Pat. No. 4,101,976, in which wavelength multiplexing recording is performed using the optical transition levels of the electron systems of organic pigment compounds and changes in the absorption band.
The materials normally used in PHB are quinizarin, pthalocyanine, porphyrin, etc., as the guest materials which are distributed in a transparent host material in the medium structure. These materials have to be cooled to the temperature of liquid helium in order to function as a PHB optical recording medium. In addition, when using PHB for optical recording there is a bleaching effect on the pigment itself by the light that is used for reading the absorbing holes which reduces the number of times the information can be read out.
Research of the physics of glasses with semiconductor fine particles has been described in "Solid State Communication", Volume 56, p. 921 (1985).
The optical non-linear response of semiconductor fine particles has been described in "Oyo Butsuri" (Japanese), Volume 55, No. 3, pp. 325-335 (1990).
Neither of these two articles describes the effect of phase changes in such semiconductor fine particles.